K8s Cpu Manager Static

Where this is already explained

• CPU Requests, Limits and CFS Throttling

  That a CPU limit is a ceiling that caps speed, so setting one is harmless hygiene. It is a per-100ms budget: a multi-threaded process can burn the whole budget in a few milliseconds and then sit completely stopped for the remaining 80-90 ms, producing tail-latency spikes on a service averaging a third of its limit. Teams then read the throttling metric as a capacity signal and buy bigger nodes, which makes it worse.

• QoS Classes: Guaranteed, Burstable, BestEffort

  That QoS is a setting, and that Guaranteed is a promise the kubelet keeps. Neither is true. You cannot set qosClass — it is derived by ComputePodQOS from the numbers you already wrote, so a sidecar injected without resources silently downgrades a carefully-Guaranteed pod to Burstable. And the kubelet's eviction ranking never looks at the class at all: rankMemoryPressure sorts on whether usage exceeds requests, then Pod Priority, then usage above requests. The familiar ordering BestEffort, Burstable, Guaranteed is a consequence of those three comparisons, not a rule, and it breaks whenever Priority disagrees — a Guaranteed pod at priority 0 is evicted before a Burstable pod at priority 1000.